Many temperature controlled commercial enclosed spaces need to be equipped with pressure relief ports or vents which are sometimes referred to as ventilators or ventilator ports. This is particularly true where the sealed space is subjected to temperature related air volume variations that must be relieved.
Cold rooms typically have a neutral air pressure. To achieve the neutral air pressure the cold room is fitted with passive ports or vents. However existing passive pressure relief ports, meaning those without fans or blowers, have often permitted unwanted air migration where there is no significant pressure differential. With walk-in freezers this air intrusion may cause undesirable condensation and frosting. Frosting is a substantial problem that occurs as ambient warm air drawn into a low temperature chamber releases significant amounts of moisture relative to the change in dew point of the air at high and low temperatures. Air is drawn through the port after each door opening cycle as the warm air that entered the enclosure cools and contracts. If venting does not occur, a partial vacuum results within the enclosure which makes it difficult to reopen the door. In extreme cases, the enclosures can even collapse.
A temperature rise in the enclosure between cooling cycles, and especially during a defrost cycle, creates a need to vent air to the exterior to prevent pressure buildup. Again, failure to vent this pressure, with adequate relief capacity, can cause the chamber to rupture.
Passive pressure relief ports are in wide commercial use today. Large structures require the movement of a large amount of air to equalize the pressure between the interior and the exterior of the enclosure. Existing commercial use vents can be either a large sized vent or a gang of small sized vents. This large amount of air movement carries with it a large amount of moisture. This moisture can condense almost immediately upon contact with the cold air and cold surfaces of the enclosure. If this occurs, a large ice block may form on the interior wall, which may eventually block the inflow of air through the port. This large ice block may also pose a potential danger to someone should it fall from the wall. Also, the use of large vents within small rooms causes a low velocity flow of air to enter the room. This low velocity air flow is more susceptible to freezing the moisture within the airflow upon entering the cold room.
Another problem with cold rooms is that high negative pressure may be dangerous as the warm air entering the cold room enters the cold room with the entrance of a person. The entering warm air subsequently cools and creates a negative pressure within the cold room. This negative pressure may hold the door in a closed position until the pressure within the room normalizes. A person within the cold room may become panicked when unable to open the door. Today's vents alleviate small amounts of incoming warm air, but are inadequate to deal quickly with large volumes of warm air associated with multiple door entries or large sliding doors.
Another problem is the icing of certain valves associated with vents of cold rooms. Moisture entering the cold room may condense as ice upon the valves, thereby preventing them from functioning properly. One solution to this problem has been to simply chip the ice off the valve or remove it with the use of a heat gun. These solutions are time consuming and inadequate as it may damage the vent, cause bodily injury, and be only effective once the problem is discovered. As such, some vents have included resistive heaters. However, should the heater fail the problem will go unresolved until the vent heater is repaired.
Yet another problem with some static valves has been that they operate and are adjusted to open at a select pressure gravitationally by adjusting the weight of a movable valve portion (poppet valve), i.e., the valves are gravitationally set and operated by their own weight, as shown in U.S. Pat. No. 6,176,776. However, large air movements, such as wind or even a door closing, may cause the valve to open or flutter. This fluttering of the valve may cause it to open unnecessarily when a need for ventilation does not truly exist. The opening may also cause the valve to remain open for more time than necessary, thereby creating an icing of the valve which increases over time due to the valve remaining in an open condition.
The adjusting of the pressure by having different sized weights also increases costs associated with the vent. The different sizing of components increases the amount of inventory a supplier must carry, increase the number of components required to assemble the vent, and creates a potential for mistakenly utilizing the wrong component.
Accordingly, it is seen that a need exists for a pressure release vent that prevents the formation of ice, is not gravitationally operated, and which allows for different amounts of air flow. It thus is to be provision of such a vent that the present invention is primarily directed